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  本文關(guān)鍵詞：水和二氧化碳的激光吸收光譜研究　出處：《太原科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 氣體檢測 近紅外吸收光譜 免校準(zhǔn)理論 波長調(diào)制 歸一化二次諧波

【摘要】：工業(yè)革命以來,由于人類大肆向空氣中排放二氧化碳等溫室氣體,已造成全球氣候變暖,極地冰川融化,極端天氣頻發(fā)等一系列問題。如何減少溫室氣體的排放成為全人類亟待解決的問題,而溫室氣體的濃度監(jiān)測是節(jié)能減排的重要環(huán)節(jié)之一。用于氣體檢測的方法可分為傳統(tǒng)法和激光光譜法,與傳統(tǒng)的氣體檢測方法相比,激光吸收光譜法有無需采樣進(jìn)行檢測,能直接實時監(jiān)測、操作簡便、實驗過程易于控制等優(yōu)勢,并具有較高的探測靈敏度,因此是目前應(yīng)用研究的熱點(diǎn)之一。本文在對吸收光譜技術(shù)理論研究的基礎(chǔ)上,采用長光程吸收和諧波檢測技術(shù),搭建了氣體檢測實驗系統(tǒng),進(jìn)行二氧化碳和水的吸收光譜研究,并對差分吸收探測電路提出了改進(jìn)。理論上,研究諧波信號與調(diào)制幅度的關(guān)系,通過理論計算,得出二次諧波峰值與氣體濃度成一定的線性關(guān)系。本文采用歸一化的二次諧波信號實現(xiàn)免校準(zhǔn)測量,此方法可以消去光源波動以及其它光電器件的電流漂移等不穩(wěn)定性噪聲。對激光器的溫度和電流調(diào)諧特性進(jìn)行試驗,分析頻率調(diào)制幅度對諧波信號的影響,調(diào)節(jié)實驗參數(shù),在波形最優(yōu)的情況下進(jìn)行實驗。利用長光程波長調(diào)制光譜技術(shù)測量了不同濃度的二氧化碳,分別獲取其直接吸收以及一次、二次諧波信號。利用Origin軟件對采集到的信號進(jìn)行去背景、擬合等處理。由歸一化的二次諧波與氣體濃度的關(guān)系,計算氣體濃度。分析計算濃度與標(biāo)準(zhǔn)濃度的偏差,檢驗氣體檢測系統(tǒng)的可行性。并對水分子在12252-12312 cm-1這個弱吸收波段的吸收譜線進(jìn)行測量,共測到了43條吸收譜線,對測得的數(shù)據(jù)進(jìn)行擬合,得到伏格特線寬和洛倫茲線寬,與Hitran譜線數(shù)據(jù)庫的數(shù)據(jù)吻合較好;將各擬合譜線的中心頻率和Hitran庫進(jìn)行比對,偏差較小,驗證系統(tǒng)具有較好的探測精度。
[Abstract]:Since the Industrial Revolution, human beings have emitted greenhouse gases such as carbon dioxide into the air, which has caused global warming and melting of polar glaciers. How to reduce greenhouse gas emissions has become an urgent problem for all mankind. The concentration monitoring of greenhouse gas is one of the important links of energy saving and emission reduction. The methods used in gas detection can be divided into traditional method and laser spectrum method, compared with the traditional gas detection method. Laser absorption spectrometry has the advantages of no sampling, direct real-time monitoring, simple operation, easy control of the experimental process, and high detection sensitivity. Therefore, it is one of the hotspots of application research. Based on the theoretical research of absorption spectrum technology, this paper builds a gas detection experimental system using long optical path absorption and harmonic detection technology. The absorption spectrum of carbon dioxide and water is studied, and the differential absorption detection circuit is improved. Theoretically, the relationship between harmonic signal and modulation amplitude is studied and calculated theoretically. The linear relationship between the second harmonic peak and the gas concentration is obtained. In this paper, the normalized second harmonic signal is used to realize the calibration free measurement. This method can eliminate the unstable noise such as the fluctuation of light source and the current drift of other optoelectronic devices. The temperature and current tuning characteristics of the laser are tested and the influence of the amplitude of frequency modulation on the harmonic signal is analyzed. By adjusting the experimental parameters, the experiment was carried out under the condition of optimal waveform. Different concentrations of carbon dioxide were measured by long path wavelength modulation spectroscopy, and the direct absorption and one time absorption were obtained respectively. The second harmonic signal is processed by using Origin software to remove background and fit the signal. The relationship between the normalized second harmonic and gas concentration is discussed. Calculate the gas concentration. Analyze the deviation between the calculated concentration and the standard concentration. To test the feasibility of the gas detection system, and to measure the absorption lines of water molecules at 12252-12312 cm-1, a total of 43 absorption lines have been measured. By fitting the measured data, the volt linewidth and Lorentz linewidth are obtained, which are in good agreement with the data of Hitran spectral line database. The center frequency of each fitting line is compared with the Hitran library, the deviation is small, and the system has good detection accuracy.
【學(xué)位授予單位】：太原科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：X831;TN249

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本文編號：1363649